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The .338-06 is a longer case than the 9.3 which would mean setting the barrel back one thread perhaps as well as re-boring the barrel.

Sorry, but you don't know what you're talking about. While the .338-06's case is slightly longer than the 9.3x62's, that doesn't matter because the 9.3's neck and bore are so much larger that reboring eliminates the .338-06's neck.

Thanks JB!

Looking at some of the chamber specs for the .338-06 show a diameter of the chamber as .369", .370" at the mouth. The 9.3 x 62 has a bore of .366". As the mouth on the 9.3 is shorter than the end of the neck on the .338-06 chamber, then surely part of the free-bore on the 9.3 will be .369 or .370 instead of .366" if you don't set the barrel back?

Odd, my AI case in the Mauser action required modification to the rails and the feed ramp. While my 700 did not. Further my pre-64 Brown Whelen would have required the same modifications as the Mauser. After setting the barrel back and chambered in 35 Whelen it fed fine.

The 30-30 case does benefit from the AI process as it does add more than 10% to overall case capacity, the squaring of the case reduces bolt head thrust. Case trimming, a pain in a regular 30-30 case is happily reduced greatly.

Riflehunter,

The standard throat ("freebore") of the 9.3x62 is a taper over an inch long, starting at .369 just in front of the mouth. A lot of old smokeless rifle cartridges had similar throats, to accommodate the shanks of the long, heavy round-nosed bullets used in those days.

The difference in case length between the .338-06 and 9.3x62 is .053", basically 1/20th of an inch. So yeah, depending on the original .338-06 chamber, there could be a very slight about of "enlargement" of the 9.3x62's very long throat just in front of the chamber--but I doubt it would make enough difference in accuracy to take the extra step of setting the barrel back a thread.

As long as the reduction in case taper doesn’t impair feeding, Go for it .
Moving the shoulder forward is also a possibility, as these case headspaces on the rim. Notwithstanding Feed n Function of course.

In the .303 British, reducing taper to the Epps / Ackley Improved doesn’t always work well with SMLE’s tapered box magazines.

The shoulder diameter expands from .441” to .454” , so yes virtually the same reduction in taper. After improving the point of the shoulder also moves forward.

The .280 Rem case has the point of the shoulder .050” further forward so it couldn’t be inadvertently chambered & fired in a 270 Win.
So slightly more volume to improve upon in a 280 Improved.

The Improvement starts from the point of contact at the neck shoulder junction.
That cone is larger than the standard case ( 17.5 degree, .441” diameter base ) , vice 40 degree .454” Ackley Improved.

Mo Bigga, Mo Betta !

I own a few AI’s: 280, 22-250, 375 Whelen, 375 H&H

My 22-250 AI, I think is worth it. Basically a 220 Swift in a better case (IMHO). It’s also one of my more accurate rifles < 1/2 MOA. It also shot 22-250 ammo in it accurately. When a fellow has a very accurate rifle to start with he likes the cartridge. Ask a certain writer what he thinks of a 270…

I like the 375 Whelen AI. There’s plenty of work making the brass at any rate. The dies were more available as was the reamer.

The others I have a luke-warm feeling. They are OK, but for me not worth the bother. Once done and cases formed they are probably “better”. But the 280 AI brass I’ve found is expensive and forming cost time and money. The H&H shoots the standard H&H ammo ok. I have no real need for the extra fps in the H&H and I don’t shoot it often enough to worry about stretching. I have not tried working up a load with standard 280 in the AI chamber.

All in all there are a few cases I think would benefit. They include 243, 30-30, 30-40, 303 Brit - I have all these and have not bothered “improving” them. Maybe if they were my main rifles I might of.

B - Seems like magazine & feeding issues are as important as any velocity improvement. Especially in the rimmed cases.

Does your 375 H&H Improved equal Weatherby or Ruger 375 ?

My 375 Improved is a solid increase over H&H and runs on peer with Wby numbers.

The Weatherby case will chamber in the 375H&H AI. Weatherby rifles are often free bored, so it’s pretty close.
The Ruger is pretty close too - going by memory - I think the Ruger may have a little larger capacity. All in all maybe 100 fps max between any of them.

I was looking for a 375 H&H when I came across this Pre-64 Model 70 chambered in the AI version. The rifle is pristine otherwise and would have brought much more money if the chamber hadn’t been messed with. I have quick detachable Leupold bases and rings along with a Pre-64 300 H&H set up identically with one spare scope and rings that will fit either. I was thinking at the time that I might still be able to safari with these rifles. I’m guessing now if I safari that might be in Texas at an exotic game ranch.

Fooled around with a .375 Weatherby some years ago, built by Dave Gentry--which is very similar to the .375 H&H AI.

Most of the "extra" velocity (once again) comes from higher pressure, not the relatively small amount of extra powder room. And it also comes at the "price" of extra recoil--when hundreds of thousands of hunters over more than 100 years have found the .375 H&H quite adequate.

I am not against new cartridges, and in fact have become quite fond of many, including the 6.5 PRC. But if I want to step up from .375 H&H performance would go to a larger caliber, say a .416 with 400-grain bullets.

What game, and build would this 416 target ?

Alaska or Africa

Rigby , or Ruger ? Or …

I looked at a BRNO 602 recently with an eye towards a LR 26” 338 Lapua ,
or 300 Norma build

416 takeoff barrel + 602 stock could be available.

I would have been happy with the 375 H&H too. I don’t try for maximum velocity, I like it when the holes in the paper come together, more so than big numbers on the chronograph.
My Ruger 416 Rigby gave me recoil head aches and right away! Granted I only tried 400 grain solids and they were full loads for a Rigby. I had thought about shooting cast bullets in that Ruger, but I decided to let it go instead. I toy with the idea of a 416 Remington or Taylor. My cousin has a 416 Remington - I’ll shoot it before I buy one.
But to tell the truth that 375 H&H AI is likely a more potent cartridge than what I’ll ever need.
I had a standard 375 H&H that evidently didn’t fit me well as felt recoil was greater than my Winchester, so I let that go I’ll probably have that on my estate sale unless one of my kids want it.

I seem to be the main person to be whining about poorly fit stocks…

Ha, Recoil headaches are why we have 6 mm CM !
And Toyota LandCruisers to tote these +40 pop-guns around

I like a StandUp bench for those beasts, Plugs & Muffs too. Gloves help

Same here Bugger. I had a P64 300 that was rechambered to 300 Wby but just wouldn’t shoot so I sent it to JES and he made my 375 Improved with a 1-10 twist. It’s very accurate with H&H loads or even factory ammo.





I use 75 grains of IMR4350 to form cases. They come outta my gun at 2450 but I think I could hunt happily with that combo if needed



I used it for a charging whitetail one day..

B : Those Yearlings can be surprisingly feisty !

I’m seriously contemplating upgrading my 338’06 to something with more frontal area to crush these Rogues more effectively.

i ai several calibers .no more case stretch.